1. Field of the Invention
The present invention relates to a primer coating for a polyester film to be primarily employed as a photographic film. The primer coating composition is applied to at least one side of a polyester film to improve the bonding between the film and one or more gelatin layers. The primer coating consists of a copolyester composition which is water-dispersible and suitable surfactant. It has been found that this primer coating composition is excellent for use in photographic films and yields superior adhesion performance over known aqueous-based photographic films. It has also been found that the primer coated film may be employed for non-photographic uses such as for diazo film, copier film, and drafting film.
The present invention also relates to a primed film with a novel gelatin/aziridine coating which is compatible with a light sensitive photographic composition. The gelatin/aziridine coating not only bonds well with the primer coating mentioned above, but also bonds to a light sensitive photographic composition. The primary purpose of the aziridine is to adhere a gelatin layer to the primer coating. Without the primer coating of the present invention, the gelatinous/aziridine coating would not satisfactorily bond to the polymeric film.
2. Prior Art
Photographic films are well known and are conventionally based on polyester substrates. Water soluble coatings applied to polyester films achieve adhesion between the polymeric film and one or more gelatin coatings. These films employ a water dispersible copolyester primer coating composition comprising a polyester portion and a sulfomonomer portion.
U.S. Pat. No. 4,394,442 to Miller, discloses a photographic film having a polyester film base with a water soluble copolyester primer coating and overcoated with a gelatin containing layer. The copolyester layer includes a sulfonated monomer pendant from a dicarboxylic nucleus of the type described herein.
U.S. Pat. No. 4,181,528 to Work, III et al discloses improved adhesion of a photographic emulsion to a polyester film base in which the primer coating contains a water soluble polyester, a gelatin, and a polyfunctional aziridine. It is contemplated that this primed polyester film is then suitable for application of a photographic gelatin layer. The primer coating is applied off-line (not during the manufacturing process for forming the polyester film). Additionally, the primed film does not always pass the wet-adhesion test that is necessary to have a suitable photographic film.
Other U.S. Pat. Nos. 4,252,885 and 4,304,851 issued to McGrail et al disclose a light sensitive photographic film produced by coating polyester films with an aqueous dispersion of copolyesters. The photographic film disclosed is directly adherable to photographic emulsions or other gelatin-containing layers.
British Patent 1,264,338 discloses an in-line coated polyester film (coated during the manufacturing process of the film) for photographic films in which a water-dispersible copolyester primer coating may be applied. In particular, this reference mentions those water dispersible polymeric based coatings described in the following British patent.
British Patent 1,088,984 discloses a treatment of polyester film by coating it in-line with a water dispersible copolyester containing a sulfomonomer group.
U.S. Pat. No. 4,493,872 to Funderburk et al (assigned to the present assignee) discloses a water-dispersible copolyester primer coating which may be applied to a polymeric film such as polyamides, polyolefin, polysulfones, polyacetal, polycarbonate and polyester (such as polyethylene terephthalate). As disclosed by this reference, the copolyester coating composition, when applied to a polymeric support, provides excellent adhesion between the polymeric support and a subsequently applied metallic coating. The copolyester primer coating consists of one or more dicarboxylic acids and at least one sulfomonomer containing a sulfonated group attached to a dicarboxylic aromatic nucleus.
Other patents assigned to the present assignee which also disclose a water soluble or water-dispersible copolyester, comprising one or more dicarboxylic acids and at least one sulfomonomer containing a sulfonate group attached to a dicarboxylic aromatic nucleus are U.S. Pat. No. 4,476,189; U.S. Pat. No. 4,525,419; U.S. Pat. No. 4,585,687; and U.S. Pat. No. 4,745,019, all of which are issued to Posey et al. These patents disclose various dicarboxylic acids which are different from those set forth in Funderburk et al.
Although several of the prior art references mention water dispersible copolyester primer coatings, and other references disclose that such coatings are suitable for photographic usage, there continues to be a need for an improved photographic film employing aqueous based coatings.
It is an aspect of the present invention to provide a suitable aqueous based primer coating composition for photographic film, as well as for non-photographic applications such as diazo films, copier films, drafting films, etc.
It is an object of the present invention to provide a polyester film coated with the primer coating composition described herein, which would be suitable for one or more photographic gelatinous layers.
Another aspect of the present invention is to provide a photographic film in which a polyester substrate having the primer coating composition of the present invention applied thereon and one or more gelatinous layers, including a light sensitive or photographic gelatinous layer, is commercially viable.
It is an object of the present invention to provide a process for priming a photographic film with the primer coating composition of the present invention to provide adequate adherence between the polyester film and one or more gelatinous layers for photographic usage.